The present invention relates to an electrode containing an ambient temperature molten salt and a method of fabricating it, and a battery. The present invention further relates to a (coating) mixture suitable for forming a cathode and a cathode formed from the mixture, and a battery. The present invention further relates to a (coating) mixture suitable for forming a lamination type stacked battery and an electrode formed from the mixture, and a battery.
In recent years, downsizing and weight saving of portable electronic devices typified by a mobile phone, a PDA (personal digital assistant), and a notebook personal computer have been actively promoted. As part thereof, improving the energy density of batteries, in particular secondary batteries as the driving power source thereof has been strongly aspired.
To improve the energy density of the secondary battery with the small volume and the small mass, the voltage per one battery should be high. From such a view point, in recent years, a nonaqueous electrolytic solution battery using, for example, a lithium-based composite metal oxide as a cathode active material and using a carbon material capable of inserting lithium or lithium ions as an anode active material has attracted attention. For example, a lithium ion secondary battery in which a cathode plate using a lithium composite oxide made of LiCoO2 or the like as a cathode material and an anode plate using a carbon material or the like that inserts and extracts lithium ions as an anode material are layered with a nonaqueous electrolyte in between has been known.
As the lithium ion battery, a spirally wound type battery in which a strip-shaped cathode electrode and a strip-shaped anode electrode are layered with a separator in between and then spirally wound to form a battery element, and the battery element is contained in a package container; and a lamination type secondary battery in which a flat cathode electrode and a flat anode electrode are layered with a separator in between to form a laminated body as a battery element, and the battery element is contained in a package container have been known.
In general, the cathode plate of the lithium ion secondary battery is manufactured by coating a current collector with cathode mixture slurry containing the foregoing lithium composite oxide (cathode active material), a binder, and an organic solvent, and then drying the cathode mixture slurry. As the binder, a vinylidene fluoride-based polymer, an acrylonitrile-based polymer or the like that has the low resistivity, the favorable battery characteristics, and the relatively superior formability is preferable and practically used.
The technique for the lithium ion secondary battery has been already developed to the degree close to the theoretical capacity. Thus, as a means for further improving the energy density of the lithium ion secondary battery, it is considered to increase the ratio of the active material layer in the battery by increasing the thickness of the active material layer and to decrease the ratio of the current collector and the ratio of the separator (Patent Document 1).
Further, to improve the energy density of the lithium ion secondary battery, it is considered to improve the capacity per unit weight of the electrode material. In recent years, a lithium ion secondary battery using a cathode active material having a main component of a lithium nickel composite oxide containing at least lithium element and nickel element such as LiNiO2, and LiNixCoyO2 instead of LiCoO2 has been developed. The capacity per unit weight of the lithium nickel composite oxide (180 to 200 mAh/g) is considerably larger than the capacity per unit weight of LiCoO2 (145 to 150 mAh/g).
Patent Document 1: Japanese Unexamined Patent Application Publication No. 9-204936